The Plant Hormone Gibberellin

Gibberellin (GA) was first identified in the pathogenic fungus Gibberella fujikuroi, which causes a disease in rice called ‘foolish-seedling’.

By producing large quantities of GA, the plants become long and slender, are incapable of supporting their own weight, and are chlorotic and partially infertile .

Further research established GA as a hormone that is essential for many developmental processes in plants, among them are seed germination; organ elongation and expansion through cell growth; trichome development; transition from vegetative to reproductive growth; and flower, seed, and fruit development .

GA manipulation in agriculture is common practice; the best-known contribution of GA manipulations to agriculture is the introduction of dwarfing alleles into staple crops. This manipulation resulted in one of the cornerstones of the so-called ‘green revolution’ and led to a massive increase in global wheat and rice yields. Identification of the genes responsible for these traits showed that the encoded proteins interfere with the action or production of GA .

Among more than 130 GAs identified in plants, fungi, and bacteria to date, only a subset, namely GA1, GA3, GA4, and GA7 are thought to function as bioactive hormones .

Additional forms of GA that exist in plants are precursors of the bioactive forms or deactivated metabolites .